When to use ‘npm start’ and when to use ‘ng serve’?

ng serve serves an Angular project via a development server

npm start runs an arbitrary command specified in the package’s “start”
property of its “scripts” object. If no “start” property is specified
on the “scripts” object, it will run node server.js.

It seems like ng serve starts the embedded server whereas npm start starts the Node servers.

Can someone throw some light on it?